1. Field of the invention
The present invention relates to a handgrip supporting mechanism for an electric apparatus, such as a surveying device.
2. Description of the Related Art
As surveying devices for measuring the azimuth, vertical and horizontal angles of an object point, a theodolite and a transit have been widely used as angle measuring devices.
In this type of surveying device, a pointing telescope for aiming at an object point is provided in such a manner that the pointing telescope is horizontally and vertically rotatable about horizontal and vertical axes. The surveying device is provided with a horizontal and vertical rotation angle detecting means (such as encoders) to detect an angle of rotation of the pointing telescope about the horizontal and vertical axes, respectively. According to the detected rotational angles, an azimuth angle of an object point is surveyed.
Recently, a device called a total station which is the combination of an electro-optical distance meter and an electronic theodolite has been practically used. The electro-optical distance meter is arranged to measure a distance to an object point with a round-trip light travelling time.
In this type of surveying device, what is obtained at first hand is rotational angle information of the pointing telescope. It is therefore necessary to detect an attitude of the surveying device itself.
Because of this requirement to obtain attitude information, the surveying device has been equipped with, for example, a two-axis automatic inclination correction sensor. It should be understood that detected information from such a sensor may directly influence the precision of the surveyed results. Accordingly, a sensor such as a two-axis automatic inclination correction sensor is mounted to the surveying device with high precision.
Also, for the purpose of carrying the surveying device, a handgrip is mounted at the upper part of the device.
The handgrip comprises a handle with a predetermined length, and a pair of mounting portions which are respectively extended from each end of the handle to the body of the surveying device. The mounting portions are detachably attached to the body with screws.
However, as surveying devices in general comprise various members made of different materials, and a handgrip is usually made of a material different from that of the surveying device, due to the differences in the thermal expansion ratios of the material of the handgrip and that of the surveying device, there may be a dimensional discrepancy in the extending direction of the handgrip and the surveying device when an ambient temperature changes.
As a result, when distortion might occur due to the force caused by the differences of thermal expansion ratios, the inclination detecting sensor changes the attitude, and an error may possibly occur.
Also, there may be a case where a handgrip is unnecessary when the surveying device is being operated. In such a case the handgrip is removed from the surveying device and then reattached. In this case, if the handgrip is removed in an environment where the ambient temperature is -20.degree. C., then reattached after the surveying device has been carried to a new environment where the ambient temperature is 30.degree. C., the resulting differences in thermal expansion ratios will cause a force to be applied to the handgrip and the surveying device, and will cause possible error.
Conventionally, the location of the inclination detecting sensor is carefully selected so that the inclination detecting sensor is not influenced by this distortion, but efforts to provide a better location of the inclination detecting sensor have so far been unsuccessful. Also, as the location of the inclination detection sensor is. limited, there is less freedom in design-work.
The present invention was created in order to solve these kinds of drawbacks which have been experienced in the conventional surveying devices.